West African leaders are holding a crucial summit in Nigeria's capital Abuja, focusing on the morale-sapping departure of Mali, Burkina Faso and Niger from their 15-member bloc Ecowas.

Few think the military rulers of the three dissident states can be persuaded to pause or reverse their decision.

While faced with this blow to regional unity, West Africa is also poised to start work on a 1,028km (689 miles) highway from Ivory Coast's main city Abidjan - through Ghana, Togo and Benin - to Nigeria's biggest city Lagos.

Construction is supposed to start in 2026 and pledges of $15.6bn (£12.3bn) have already been mobilised from a range of funders and investors.

Just as Western Europe matched the Soviet-led communist bloc with a "Common Market" that later evolved into today's trading powerhouse, the European Union (EU), so Ecowas may find that a drive for prosperity and growth proves to be its most effective response to the wave of military coups and nationalism that have swept across the region since 2020.

The plan to build a modern transport corridor along the West African coast was originally approved eight years ago - long before the coups that have overturned civilian rule in Mali, Burkina Faso and Niger.

Preparatory studies, led by the African Development Bank, were commissioned.

But when these were presented last month, the timing could hardly have come at a better moment for reinvigorating the battered self-confidence of Ecowas (Economic Community of West African States).

Neither traditional diplomacy, nor sanctions, nor even the threat of military intervention in Niger, had managed to push the juntas into organising elections and restoring civilian government, as required by Ecowas governance rules.

The defiant regimes declared they would leave the 15-member bloc altogether.

They have subsequently spurned the remaining members' efforts to persuade them to stay, although the Ecowas envoy, Senegal's new, young President Bassirou Diomaye Faye, who shares their nationalistic outlook, is still trying.

Until this crisis, Ecowas was Africa's most cohesive and politically integrated regional grouping, with a creditable record of crisis management and even the deployment of peacekeepers in troubled member states.

With the departure of Mali, Burkina and Niger, the bloc will lose 76 million of its 446 million people and more than half its total geographical land area, with the loss of vast tracts of the Sahara – a painful blow to prestige and self-belief.

The shock of the three countries' withdrawal may boost those pushing for tougher governance and democracy rules.

Meanwhile, the ambitious coastal transport corridor project, conceived to support economic development, will also serve a political purpose - demonstrating the remaining member countries' capacity to work together and accelerating the trade growth and investment attraction of coastal urban West Africa, already the most prosperous part of this vast region.

And just as the EU's wealth and dynamism proved a powerful attraction for former communist states, perhaps rising prosperity across Ecowas will eventually entice the now disenchanted further north states into rejoining the bloc.

Construction of the proposed four-to-six lane motorway is forecast to create 70,000 jobs, with completion ambitiously targeted for 2030.

And the plan is to acquire a sufficiently broad strip of land along the route to later accommodate a new railway line, linking the big port cities along the Gulf of Guinea. Existing rail routes extend inland, but there is no rail line along the coast.

The road will connect many of West Africa's largest cities - Abidjan, with 8.3 million people, Accra (4 million), Lomé (2 million), Cotonou (2.6 million) and Lagos, estimated at close to 20 million or perhaps even more.

Several of the cities are key gateway ports for the flow of trade in and out of the region.

Already the bureaucratic hassles and risks of petty corruption that have so often complicated life for drivers passing from one country to the next are beginning to wane.

At many border crossings, modern one-stop frontier posts, where officials from both countries work side by side to check passports and transit documents, have replaced the assorted huts where drivers and passengers queued at a succession of counters while one set of border police and customs officers after another laboriously worked their way through the formalities.

And now the proposed highway and rail line promise to further speed the flow of trade and travel between the coastal economies, boosting competitiveness and integration and transforming the region's attraction for investors - just as the EU transformed trade and development across the European continent.

And that process of economic and administrative integration of course had enormous political consequences.

It acted as a powerful incentive for countries still outside the bloc to improve economic governance, strengthen democracy and tackle corruption, in the hope of qualifying for membership.

Perhaps Ecowas can emulate this precedent, and lure the dissident states into re-joining, particularly if flagship projects such as the transport corridor give a real fillip to growth.

For not only do Mali, Niger and Burkina face severe development and security challenges, but they are also all landlocked, and heavily dependent on their coastal neighbours, through transport, trade and labour migration.

Huge volumes of trade, formal and informal, flow across the borders.

Livestock from the three countries in the Sahel is exported on the hoof to feed city dwellers in Dakar, Abidjan and Lagos.

Onions and potatoes grown in Niger's arid climate are prized by coastal household shoppers, while Ivorian, Ghanaian and Nigerian manufactured goods are exported in the opposite direction.

Millions of Burkinabès and Malians are settled in Ivory Coast, a mainstay of the workforce for its cocoa plantations.

Moreover, the coup leaders are not pulling out of the West African CFA franc, an eight-country single currency, backed by France, that hampers competitiveness but provides a solid defence against inflation and monetary instability.

Yet these deep ties between the Sahelian countries and coastal West Africa were not sufficient to deter the military regimes in Mali, Burkina and Niger from announcing their withdrawal from Ecowas.

Hostility to the bloc, which they portray as bullying and arrogant, has paid political dividends, boosting their popularity at home. And Morocco talks of opening up an alternative trade corridor to its Atlantic ports, which could broaden the options.

But if the remaining Ecowas countries can accelerate their own drive for prosperity, pruning back trade barriers and pressing forward with breakthrough projects such as the coastal highway and rail line, then gradually they may salve today's political bruises and mistrusts and draw the Sahel states back into a reunified West African regional identity.

Paul Melly is a consulting fellow with the Africa Programme at Chatham House in London.